Sup rat en tonal Deep Brain Arteriovenous Malformations: Caudothalamic 261

Caudothalamic Arteriovenous Malformations

4.49

Special Caudothalamic arteriovenous malforma-
Considerations tions (AVMs) are located lateral and interi-
or to the lateral horn of the lateral ventricle.
Laterally placed lesions medial to the inter-
nal capsule are most accessible. Dorso-
medial and ventromedial Caudothalamic
AVMs are more difficult to approach owing
to involvement of the limbic system, hypo-
thalamus, and deep venous system.

The arterial supply arises from the an-
terior and posterior choroidal arteries,
which enter the ventricle through the ante-
rior and posterior choroidal fissures. Less
accessible feeders located deep at the AVM
base are thalamoperforating arteries from
A,, M,, and P,. These perforating arteries
pass directly through the parenchyma of
the caudate nucleus and thalamus to reach

the malformation. Venous drainage is to
subependymal, caudate, and thalamostriate
veins and ultimately drains through the in-
ternal cerebral and basal veins.

Most Caudothalamic malformations pre-
sent with parenchyma! hemorrhage. Mag-
netic resonance imaging (MRI) is helpful in
identifying small hematomas that may be
clinically silent. MRI also supplements an-
giography by defining the relationship of a
hematoma to the malformation and the rela-
tionship of the malformation nidus to deep
brain structures. Angiographic images are
assessed for evidence of pedicular and in-
tranida! aneurysms thai may be the actual
source of hemorrhage in some cases.

262

Arteriovenous Malformations of the Brain

Stereotactic radiosurgery is a valid
consideralion for critically located lesions
in the hypothalamic or capsular region.
When a major hemorrhage has occurred,
surgical extirpation is indicated. Parenchy-
mal hematoma helps to dissect and partially
define the lesion. Preopcrative emboliza-
tion of the perforating arteries arising from
A,, M|, and P, facilitates surgical resection.
In our experience, the operative morbidity
has decreased to the extent that small le-
sions can be removed in patients who are
neurologically intact. Approaches to cau-
dothalamic AVMs include the trans-
callosal-transventricular, transcortical-trans-
ventricular, and transsylvian. The trans-
sylvian approach is reserved for lesions
presenting laterally in the area of the exter-
nal capsule.

performed with the patient in the supine
position. The thorax is elevated 15 degrees
and a gelatin roll is placed under the left
shoulder. The head is maintained in a radio-
lucent head-fixation device and rotated to
the right (lesion side down) until the sagittal
suture is parallel to the floor. The inguinal
region is prepared for intraoperative angi-
ography.

Approach A parasagittal craniotomy as for a standard
transcallosal approach (see Chapter I) is

4.50

4.50 The AVM illustrated in
this coronal section is dorsomedial, located
in the caudate nucleus and thalamus. The
nidus and hematoma extend into the lateral
wall of the third ventricle.

Supratentorial Deep Brain Arteriovenous Malformations: Caudothalamic 263

Foramen of
Monro

Choroid
plexus

Fornix

4.51

4.51 Retractors are placed
on either side of the pericallosal arteries. A
2-cm incision is made in the corpus cal-
losum. The foramen of Monro of the right
lateral ventricle is visualized as cerebrospi-
nal fluid is aspirated from the ventricle.

4.52 The AVM is intertwined
with choroid plexus and draining veins. The
patient's systemic blood pressure is low-
ered to 55 mmHg mean arterial pressure as
dissection of the nidus begins at its lateral
border. Small feeding arteries and ependy-
mal veins are coagulated and incised.

Thalamostriate
vein

4.52

Arteriovenous Malformations of the Brain

4.53

4.53 Progressive dissection
of the nidus proceeds along its lateral bor-
der until the choroid plexus and malforma-
tion can be reflected medially.

4.54 Posterior thalamostriate
and ependymal veins are coagulated and in-
cised.

4.55 The distal choroid
plexus is coagulated and incised.

Supratentorial Deep Brain Aneriovenous Malformations: Caudothalamic 265

4.54

Posterior

choroid

plexus

Thalamostriate
vein

4.55

266 Arteriovenous Malformations of the Brain

Septal Internal
vein cerebral
vein

4.56

4.56 The thalamostriate vein
is coagulated and cut at its junction with the
internal cerebral and caudate veins.

4.57 Inspection and intra-
operative angiography show residual mal-
formation in the wall of the third ventricle
and in the caudate anterior to the foramen
of Monro. Dissection begins in the caudate
by isolating the nidus from small perforat-
ing arteries.

Supratentorial Deep Brain Arteriovenous Malformations: Caudothalamic 267

Hematoma

Perforating arteries
from anterior and
middle cerebral arteries

4.58 Further dissection en-
ters the hematoma cavity. The remaining
nidus is separated from perforating arteries
from the middle and anterior cerebral
vessels.

4.59 Subchoroidal dissection
proceeds lateral and posterior to the fornix
and proceeds to reflect the AVM posteri-
orly along with the infernal cerebral vein
and wall of the third ventricle.

Third
ventricle

4,59

268

Arteriovenous Malformations of the Brain

4.60 The internal cerebral
vein is occluded with bipolar forceps and
cut. The nidus bed as well as the third and
lateral ventricles are inspected for residual
malformation, bleeding points, and hema-
toma. A second intraoperative angiogram
shows no residual malformation.

4.60

Closure Closure is performed as for a parasagittal
craniotomy (see Chapter I, Interhemispher-
ic Approach: Callosal).

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